This invention relates to lifting devices such as jacks and particularly to fluid pressure or pneumatic type jacks having utility in lifting cars for changing flat tires, and to the method of making such jacks.
The difficulties, dangers and general inconveniences which are characteristic of mechanical lifting devices such as jacks are commonly known. Mechanical jacks are normally multi-component structures which are expensive and which require assembly prior to use. Further, mechanical aptitude is often required during their use.
Once in use, the stability of such jacks is often unsatisfactory. The user is required to take precautionary measures to guard against the car being lifted from, coming free of contact with, and support by, the jack. Furthermore, convenient and compact storage of these mechanical jacks is a problem as is their cost of manufacture.
Alleviation of certin of the aforementioned problems attendant with mechanical jacks has been made possible with fluid pressure or pneumatic type jacks.
One of the known forms of pneumatic jacks is the barrel-shaped structure or cylindrical bag stretcher which operates on the bellows type of principal. These pneumatic jacks offer advantages in that they are of an essentially one-piece construction, are easily and conveniently storec, and have good stability and are light weight when compared with most known mechanical jacks. One disadvantage of these jacks has been their high manufacturing cost, a factor believed to have precluded a wide market acceptance of such type of jack. A typical example of such jack is disclosed in U.S. Pat. No. 3,565,398. Another disadvantage in using such devices is that it requires careful positioning of the jack beneath the car to be lifted in order to preclude inadvertent rolling of such jack and movement of the car during, or subsequent to the full inflation of the jack.
Another type of fluid pressure or pneumatic type jack is described in U.S. Pat. No. 4,036,472 to Orndorff. This jack consists of a flat, rectangular, inflatable bag fabricated from two rectangular sheets stitched at their marginal portions. An inflation chamber is created between the sheets. Each of the two sheets includes layers of rubberized, mutually parallel, supporting cords extending at a pre-selected acute angle relative to the longitudinal center line of the sheets in which they are contained. Their cords are oriented with immediately adjacent layers being in opposite directions. Such type of jack, however, is still relatively expensive to fabricate.
Efforts all over the world have been and are being made to develop improved fluid pressure or pneumatic type jacks which would require a reduced manufacturing cost. Such developmental efforts, however, have heretofore been incapable of achieving sufficiently significant advantages of inflatable jacks over mechanical jacks to create their broad market acceptance.
The present invention overcomes these difficulties by a construction which makes the jack stable in use once inflated because of its unique anti-roll feature. A rigid peripheral rim wedges the pneumatic jack into a canted position which in effect prevents the further movement of the jack. The method of making the pneumatic jack results in low manufacturing costs when compared to prior similarly constructed jacks. In one form of the invention the peripheral rim has a non-metallic edge which enhances the anti-roll feature of the jack.